1. Field of the Invention
This invention relates to a wire saw, and more particularly to a wire saw for cutting work such as a columnar semiconductor ingot, ceramics and glass into a multitude of wafers by wire rows.
2. Description of the Related Art
One of cutting devices for cutting a work such as a semiconductor ingot, ceramics and glass into thin sheet-shaped wafers is a wire saw. This wire saw is a device used in such a manner that a work is abutted against a wire running between a pair of wire reels while working solution containing abrasive grains is supplied to the wire, whereby the work is cut into wafers through the lapping action of the abrasive grains.
In recent years, the diameters of the wafers have the tendency to increase in size for example from 8 inches to 12 inches. For this reason, the wire used for cutting, longer ones is being used. For this reason, the weight of the wire reels, around which the wire is wound should necessarily have the tendency to increase in weight exceeding 100 kg.
Heretofore, the wire reels of the wire saw have been driven in a manner to transmit the rotation of a driving motors by the belt transmission.
Furthermore, as the cutting methods by use of the wire saw, there are two methods including one-way feeding cutting, in which the work is cut while the wire is caused to run only in one way, and a double-way feeding cutting, in which the work is cut while the wire is caused to run reciprocatingly. From these methods, in the case of the double-way feeding cutting, the wire reel should necessarily repeat acceleration and deceleration in a short period of time (1 to 6 sec.), so that a high acceleration torque becomes necessary due to the inertia of the wire reel.
However, if the wire reel having a large weight is driven by the driving method of the conventional belt transmission, then a motor having a high inertia should be necessary for driving the wire reel, so that a large-sized motor should be used for driving the wire reel, thus causing a problem in that a driving section becomes large-sized. Furthermore, when the acceleration or deceleration torque is high, it is deemed that the damages of the belt and the like are caused, thus raising such a problem that the period of time for the acceleration or deceleration cannot be shortened and so forth.